1. Field of the Invention
The present invention relates to a bent state holding mechanism of an endoscope.
2. Description of the Related Art
In typical endoscopes, a bendable portion control mechanism (bending mechanism) for bending a bendable portion, which is provided in the vicinity of the distal end of an insertion portion of the endoscope, by remote control is freely rotatably mounted to the control portion that is coupled to the proximal end of the insertion portion of the endoscope. Such endoscopes are provided with a bent state holding mechanism for freely switching between a bent-state holding state, where frictional resistance is exerted on the rotating operation of the bending mechanism so that the free end of the insertion portion of the endoscope remains directed toward a target affected area or the like, and a bendable-portion free state where no frictional resistance is exerted on the rotating operation of the bending mechanism, by manually rotating a bent state holding knob.
Additionally, conventional endoscopes provided with click members (tactile-response members) which provide a tactile “click” feel to the rotating operation of the bent state holding knob so that the operator of the endoscope can feel a change in state of the bent state holding knob with his/her hand when the bent state holding knob is operated to move to the aforementioned bent-state holding state and/or when the bent state holding knob is operated to move to the aforementioned bendable-portion free state (for instance, this type of endoscope is disclosed in Japanese unexamined patent publication H10-286220).
FIG. 13 shows a bent state holding mechanism of a conventional endoscope like the aforementioned conventional endoscope. This bent state holding mechanism is provided with a bent state holding knob 91 which is operated to switch between a bent-state holding state, in which frictional resistance is exerted on the rotating operation of the bending mechanism to hold a bendable portion control knob 90, which is mounted to the control portion of the endoscope to be freely rotatable about an axis X, at any given rotation position, and a bendable-portion free state in which no frictional resistance is exerted on the rotating operation of the bending mechanism. The bent state holding knob 91 is mounted to the control portion of the endoscope to be freely rotatable about the axis X.
The bent state holding mechanism is further provided with a click pin 92 and a click leaf spring 93 that are provided as click members which provide a tactile “click” feel to the rotating operation of the bent state holding knob 91 at a predetermined point in the range of rotation of the bent state holding knob 91. The click pin 92 rotates with the bent state holding knob 91 when the bent state holding knob 91 is operated to rotate, and the click leaf spring 93 is fixed to a fixing portion of the control portion to be pressed against the click pin 92 when the click pin 92 rotates.
However, as shown in FIG. 13, in the bent state holding mechanism of the conventional endoscope, the click leaf spring 93 is formed in the shape of a part of a tube surrounding the axis X so that a side of the click pin 92 is pressed against a surface of the click leaf spring 93.
Due to this structure, the thickness of the bent state holding mechanism of the conventional endoscope is great in the direction of the axis X. Accordingly, if the bent state holding mechanism is installed in an internal space of the bent state holding knob, the bent state holding knob becomes large in size and the operability thereof deteriorates. Additionally, it becomes difficult for another mechanism (e.g., a safety torque limiting mechanism for the case of an excessive force over a predetermined torque being exerted on the bendable portion control knob) to be installed in an internal space of the bendable portion control knob if so desired.